The present invention concerns a mounted assembly comprising a wheel rim, a safety support and a tire able to roll along a certain distance at zero pressure with the inside part of the tread supported by the safety support. More particularly, the invention concerns a method for lubricating the interfacial zone between the inside part of the tire tread and the support. It also concerns a lubricating device and a seal which enables said method to be put into effect, as well as a support and a reservoir that enable the method to be implemented.
Safety supports for vehicle wheels mounted with tires are well known. The document EP 0 796 747 describes an example of such a support consisting of a circular body adapted for fitting onto a wheel rim of a vehicle. The example illustrated in that document is made mainly from a vulcanized rubber mix some areas of which are reinforced, for example by metallic or textile wires or cables. Needless to say, other materials can be used to make such a support.
In general, safety supports are mounted on a wheel rim inside a tire to provide a support for the crown of the tire when it is rolling at low or zero pressure, for example after a blow-out. This avoids direct contact between the tire and the wheel rim, which generally results in rapid deterioration of the tire. Thus, supports improve the safety of the vehicle by allowing rolling for a certain time so that a suitable place where repairs can be effected may be found.
To allow rolling in conditions of low or zero pressure, it is greatly preferable to provide lubrication in order to avoid premature deterioration of the contact and friction zones, which are subjected to relatively high temperatures. Lubricants of known types, such as silicones, are used for this purpose.
A number of devices that enable such lubrication to be effected are already known. For example, the document FR 2 206 202 describes a device comprising a reservoir that can contain a lubricant. The reservoir is sealed by a thermally fusible plug whose melting point is between about 60° C. and about 120° C. When the tire is rolling while ‘flat’, the temperature increase produced by friction causes the plug to melt or at least to soften, and this unblocks the outlet. Such a device has certain functional limitations. For example, it sometimes occurs that the temperature of a tire increases even at normal pressure, up to levels that can cause the plug to melt. The lubricant is then ejected out of the reservoir and this can give rise to various types of problems, for example problems of non-uniformity, depletion of lubricant reserves, etc.
Document FR 2 654 040 describes a wheel in which a reservoir is provided that is sealed by a contact plate which releases the lubricant liquid when the tire tread comes into contact with the wheel rim. This device has the disadvantage that it releases liquid even in the event of instantaneous or transient contact, for example when the tire is subjected to an impact.
Document FR 2 654 041 describes a wheel in which a reservoir is provided in the form of a bellows sealed by a feeler: when the tire tread makes contact with the wheel rim, the feeler breaks and this then releases the lubricant liquid. Since the breaking conditions of the feeler are difficult to reproduce repetitively, breaking can take place in a range of conditions. This range embodies an uncertainty about when the lubrication will be triggered. Besides, the feeler cannot be removed because it has to be broken in order to release the liquid.